Can You See What I See?

Scientists can reconstruct a clip you're watching from information about what is happening in your brain. But does the advent of brain reading cast any new light on the nature of mind?

People are good mind readers, because they are good face readers. Are you paying attention? The answer, very often, is written all over your face.

How much better it would be, though, if we could actually get inside another person's head, to see what they see, and feel what they feel, from the inside.

To judge by recent reports, something like this may now be possible for the first time. It's old news that what you see affects your brain. In principle, then, it ought to be possible to figure out what you are seeing -- or thinking or feeling or desiring -- by looking at what is going on in your head. And this is exactly what Jack Gallant and his neuroscience group at U.C. Berkeley seem to have managed to do. They have been able to reconstruct what you are seeing -- they literally make a film clip -- just on the basis of looking at what is going on your brain.

This is not the first reported example of this kind of "brain reading." Using computer-assisted pattern recognition and the mathematics of multivariate analysis, John Dylan Haynes and his collaborators in Berlin have been able, reliably, on the basis of neural data, to determine which of two buttons a subject in a scanner has secretly decided to press. Indeed, Haynes has also shown that it is possible to know which button the subject will decide to press, even before the decision has been taken.

These are remarkable findings and there can be no doubt, as some have worried, that they raise important ethical and legal issues. But it is important to put the findings in context. When we do so, I believe, it becomes clear that they are both less interesting, and less dangerous, than people have thought.

The first thing to remember is that there is nothing new about the ability to perceive the thoughts, intentions, and feelings of other people. What a person says about what she wants or feels or needs is just one of the ways we have of telling what is playing out in her mind. To pick a humdrum example: Every time you walk or drive from one place to another, you rely on information about what the people around you see and what they intend to do. Indeed, the ability to make sense of the experience of others is one of our most basic capacities, one without which our distinct form of animal life would not be possible.

Moreover, there's nothing new about the ability to violate a person's privacy by observing them. Remarkably, we can violate a person's privacy by close observation. We can find out more about what she thinks and feels and wants than she may know herself.

So what's so special about brain reading? Well, there isn't anything special about brain reading. It's just a new way of observing a person.

Not so fast, you will object. The scary and fascinating thing about brain reading is that it allows us to know what another person is thinking or seeing without observing him or her. Brain reading technology allows us to get inside the person, to see what is happening in the brain itself, and so in the soul or very consciousness of the other. For the first time, it seems, we can bypass all the externals and make direct contact with the mind.

This is a wildly wrongheaded reading of the results and it expresses a profound misunderstanding of the nature of the mind. That we find this such a tempting way to think about the results tells us more about our culturally shared fantasies than it does about anything else.

Take a closer look at how the Gallant experiments were designed. Step 1: Scan the brains of people watching movies. Step 2: On the basis of this scan, work out a mapping between perceived stimuli and brain states. Step 3: Show the same people new movies and see what is happening in the brain. Step 4: Use the already established mapping between visual stimuli and brain states to construct a representation of the imagery -- a film clip -- that is likely producing the brain states.

There's plenty of detail I'm leaving out, but this summary is accurate enough to bring out the crucial fact that "decoding" the brain is really a process of looking at what happens in the brain as the person acts on or responds to the world. It is only in the context of the active tasks, interests, and activities of a person who is in fact dynamically responding to the world around her that the brain states have any significance for us.

My point is not that we cannot find out what you are thinking or feeling or experiencing by "reading" your brain. We can, at least in principle. My point is that what allows us to do this is our prior knowledge of you. It is only if I already know you -- if I've already mapped what happens to you and in your brain as you respond to the world around you; this is the real work of the experiment -- that I can do this.

Brain reading, then, is more like reading a person's facial expression than it is like a direct encounter with the soul. And brain reading is something we can do not because the brain is the seat of consciousness, but precisely because it is not.

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Alva Noë is a philosopher and cognitive scientist. He is the author of Out of Our Heads: Why You are Not Your Brain and Other Lessons from the Biology of Consciousness. He is now at work on a book about art and human experience.